ACE design and RHI

[omarmontes]

Hi guys!

I'm doing a redundant ACE module installation (using 7600) and I came with some design questions.

From the configurations guides, you configure a VLAN X for clients (where the traffic to be balanced arrives), and VLAN Y for servers (where the real servers are). In all the examples I've seen, the VIP address is from the client VLAN subnet, from that I wonder:

1.- Is this the only way to do this?  The 7600 supervisor knows where the VIP is because it has a BVI in that same VLAN X, so it’s directly connected. For the 7600 to reach the real server subnet, it would need a static route pointing to the ACE IP address right?

2.- In that scenario (VIP living in the Client VLAN X), RHI is not necessary right? But when the VIP is not available? What would happen then? You still need RHI so there is a "dynamic" host route for the VIP?

3.- Then in what situations would RHI it be needed? I've read that you need RHI when you don’t have the Supervisor and the ACE directly connected, but I don’t quite get this, can someone clarify?

4.- Can the VIP be a member of a different subnet? For example can it be a member of the Server VLAN Y? Or a completely different VLAN Z?, what would be the necessary changes?

Thanks a lot for your time guys, any help is greatly appreciated.

Omar M.

[Surya ARBY]

RHI is mainly used for inter site redundancy, instead of relying on DNS for your VIP HA, you rely on routing by announcing a /32 route in your OSPF backbone.

1 - yes

2 - it depends on the way you want to ensure inter site HA.

3 - the purpose is only to send a /32 route from multiple ACE clusters or sites. When your whole cluster or datacenters is down, the routing topology is built again pointing the same IP address to the new site (with playing on the OSPF cost) without any problem of DNS dead A record with client cache.
4 - No problem. You can even do it manually with a conditionnal host route defined on the upstream router (conditionned with an IP SLA sensor) redistributed into your OSPF process